1. Field of the Invention
The invention concerns a device for actuating an articulated mast, which is preferably linked to a mast base rotatable on a chassis about a vertical axes and which includes at least three mast arms, which are limitedly pivotable relative to the mast base about parallel horizontal articulation axis or an adjacent mast arm by means of respectively one drive unit, with a control device for actuation of the drive units for movement of the mast, which includes, preferably in chassis-referenced or mast-referenced coordinate system, a coordinate transformer responsive to given guiding parameters and measured angular values determined by means of angle sensors located on the mast arms for translation into articulation movement signals relevant for the drive units in accordance with a pre-determined path/slew characteristic.
2. Related Art of the Invention
Devices of this type are employed for example in large manipulators, particularly for concrete pumps. This type of large manipulator is manipulated by an operator, who is responsible, via a remote control device, both for the control of the pump as well as for the positioning of a terminal hose provided at the tip of the articulated mast. The operator must control multiple rotational degrees of freedom of the articulated mast via the associated drive units for movement of the articulated mast in the non-structured three dimensional work space, taking into consideration the construction site boundary conditions or constraints. The control of the individual axis does have the advantage that the individual mast arms can be brought respectively individually into any desired position, limited only by their pivot range. Each axis of the articulated mast or the mast base is assigned in this case a main adjustment direction of the remote control elements of the remote control device, so that in the case of the presence of three or more mast arms the operation becomes unmanageable. The operator must continuously keep an eye on both the actuated axes as well as the end hose, in order to avoid a risk of uncontrolled movement of the end hose and therewith an endangerment of the construction site personnel.
In order to simplify manipulation in this respect, a control device has already been proposed (DE-A-4306127), in which the redundant articulation axis of the articulated mast, in each rotation position of the mast base independent of the rotation axis thereof, are controlled conjunctively with one single control movement of the control element. Therein the articulated mast carries out an extension and retraction movement overseeable by the operator, wherein the elevation of the mast tip is maintained constant. In order to make this possible, this control device includes a computer supported coordinate transformer for the drive units controllable via the remote control element, via which in the one main adjustment direction of the remote control element the drive units of the articulated axes are controllable independent of the drive unit of the rotation axes of the mast base with carrying out of an extension and retraction movement of the articulated mast with predetermined height of the mast tip. In another main adjustment direction or main positioning direction the drive units of the articulated axes are controllable independent of the drive units of the rotation axis with carrying out of a raising and lowering movement of the mast tip. For optimization of the movement sequence during the extension or retraction process it is there considered to be important that the drive units of the redundant articulated axes of the articulated mast are respectively controllable in accordance with a path/slew characteristic. Included therein is that the path/slew characteristic in the coordinate transformer is modified due to the influence of bending or torsional moments acting on the individual mast arms.
In order to detect the movement sequences in the articulated mast, angular sensors are provided on the mast arms for determining the articulation angle. The individual angle sensors respectively measure only the articulation angle between two mast arms of one articulation axis. This type of angular measurement is robust, since the system is relatively stiff in the axis area and since the angle sensor provides the actual articulation angle with great precision. The axis associated measurement value is independent of the measurement values at the other axes. Thereby, one obtains a relatively simple mathematical relationship between the articulation angles on the one hand and the instantaneous position of the end hose on the other hand. One refers to this as a coordinate transformation between the articulation axis-associated angle coordinates and the chassis-based cylinder coordinates, in which the end hose of the device is being moved.
The articulation axis related angular measurement value is also independent of the bending of the individual mast arms due to the loads acting thereon. The bending must supplementally be mathematically taken into consideration. For this, one must first determine the mass of the individual arm parts and therein, in particular, filling of the associated distribution pipes with concrete. The bending is then input purely mathematically into the coordinate transformation. This is considered disadvantageous.
On the other hand, it has been found advantageous, in the dynamic respect, that the articulation axis related angular measurements do not contain any information components regarding the swivel condition itself, so that, with regard to the angular measurements, a dynamic decoupling occurs. The relatively stable axis angles thus make possible an error magnitude feedback relying on supplemental information regarding the swivel condition in the individual axes, for example, the dynamic pressure progression in associated control cylinders. Therewith, an effective oscillation damping is made possible (see DE-A-10046546).
The known device, in which the mast arm angle is measured in an articulation axis referenced chassis-based coordinate system, has the following disadvantages:    a) The assembly of the angle sensors in the area of the articulation axes is laborious, since the design provides for many components to already be located in the area of the axis, which interfere with the attachment of the angle sensor.    b) The weight of the axis-associated angle sensor inclusive of cabling is approximately 50 Kg per axis, which is relatively high.    c) With the articulation axis associated angle sensors only the articulation axes are measured, and this without taking into consideration the bending of the individual mast arms. For the bending due to the torsional moments, with and without filling of the distribution pipes with concrete, a supplemental mathematical model is necessary, which can introduce errors.